"""
Formtools Preview application.
"""
from django.http import Http404
from django.shortcuts import render_to_response
from django.template.context import RequestContext
from django.utils.crypto import constant_time_compare
from django.contrib.formtools.utils import form_hmac
AUTO_ID = 'formtools_%s' # Each form here uses this as its auto_id parameter.
[docs]class FormPreview(object):
preview_template = 'formtools/preview.html'
form_template = 'formtools/form.html'
# METHODS SUBCLASSES SHOULDN'T OVERRIDE ###################################
def __init__(self, form):
# form should be a Form class, not an instance.
self.form, self.state = form, {}
def __call__(self, request, *args, **kwargs):
stage = {'1': 'preview', '2': 'post'}.get(request.POST.get(self.unused_name('stage')), 'preview')
self.parse_params(*args, **kwargs)
try:
method = getattr(self, stage + '_' + request.method.lower())
except AttributeError:
raise Http404
return method(request)
def unused_name(self, name):
"""
Given a first-choice name, adds an underscore to the name until it
reaches a name that isn't claimed by any field in the form.
This is calculated rather than being hard-coded so that no field names
are off-limits for use in the form.
"""
while 1:
try:
self.form.base_fields[name]
except KeyError:
break # This field name isn't being used by the form.
name += '_'
return name
def preview_get(self, request):
"Displays the form"
f = self.form(auto_id=self.get_auto_id(), initial=self.get_initial(request))
return render_to_response(self.form_template,
self.get_context(request, f),
context_instance=RequestContext(request))
def preview_post(self, request):
"Validates the POST data. If valid, displays the preview page. Else, redisplays form."
f = self.form(request.POST, auto_id=self.get_auto_id())
context = self.get_context(request, f)
if f.is_valid():
self.process_preview(request, f, context)
context['hash_field'] = self.unused_name('hash')
context['hash_value'] = self.security_hash(request, f)
return render_to_response(self.preview_template, context, context_instance=RequestContext(request))
else:
return render_to_response(self.form_template, context, context_instance=RequestContext(request))
def _check_security_hash(self, token, request, form):
expected = self.security_hash(request, form)
return constant_time_compare(token, expected)
def post_post(self, request):
"Validates the POST data. If valid, calls done(). Else, redisplays form."
f = self.form(request.POST, auto_id=self.get_auto_id())
if f.is_valid():
if not self._check_security_hash(request.POST.get(self.unused_name('hash'), ''),
request, f):
return self.failed_hash(request) # Security hash failed.
return self.done(request, f.cleaned_data)
else:
return render_to_response(self.form_template,
self.get_context(request, f),
context_instance=RequestContext(request))
# METHODS SUBCLASSES MIGHT OVERRIDE IF APPROPRIATE ########################
def get_auto_id(self):
"""
Hook to override the ``auto_id`` kwarg for the form. Needed when
rendering two form previews in the same template.
"""
return AUTO_ID
def get_initial(self, request):
"""
Takes a request argument and returns a dictionary to pass to the form's
``initial`` kwarg when the form is being created from an HTTP get.
"""
return {}
def get_context(self, request, form):
"Context for template rendering."
return {'form': form, 'stage_field': self.unused_name('stage'), 'state': self.state}
def parse_params(self, *args, **kwargs):
"""
Given captured args and kwargs from the URLconf, saves something in
self.state and/or raises Http404 if necessary.
For example, this URLconf captures a user_id variable:
(r'^contact/(?P<user_id>\d{1,6})/$', MyFormPreview(MyForm)),
In this case, the kwargs variable in parse_params would be
{'user_id': 32} for a request to '/contact/32/'. You can use that
user_id to make sure it's a valid user and/or save it for later, for
use in done().
"""
pass
[docs] def process_preview(self, request, form, context):
"""
Given a validated form, performs any extra processing before displaying
the preview page, and saves any extra data in context.
"""
pass
def security_hash(self, request, form):
"""
Calculates the security hash for the given HttpRequest and Form instances.
Subclasses may want to take into account request-specific information,
such as the IP address.
"""
return form_hmac(form)
def failed_hash(self, request):
"Returns an HttpResponse in the case of an invalid security hash."
return self.preview_post(request)
# METHODS SUBCLASSES MUST OVERRIDE ########################################
def done(self, request, cleaned_data):
"""
Does something with the cleaned_data and returns an
HttpResponseRedirect.
"""
raise NotImplementedError('You must define a done() method on your %s subclass.' % self.__class__.__name__)
Feb 24, 2017